BackgroundOne of the most common reasons for poor medication adherence and associated treatment failure of triple therapy is adverse drug effect (ADEs) of medications.ObjectiveAssessment of ADEs and associated factors during H. pylori eradication therapy.MethodConsented H. pylori positive adult outpatients on standard triple therapy (proton pump inhibitor, amoxicillin and clarithromycin) were involved in this facility based follow up study from May 2016 to April 2018 at Bahir Dar city in Ethiopia. Pre-developed questionnaire and formats were used to collect sociodemographic, medical information, and patient practice data before, during, and after therapy. Bivariate and backward stepwise multivariate logistic regression was used to analyze data. P-value < 0.05 at 95%CI was considered as significant.ResultA total of 421 patients were involved in the study. Almost 80% of the patients were urban residents. Mean (±SD) age and body weight of patients were 30.63 (± 10.74) years and 56.79 (± 10.17) kg, respectively. ADE was reported from 26.1% of the patients and of all the reported ADEs, more than 85% was manifested with gastrointestinal symptoms which include gastrointestinal discomfort(39.1%), nausea (13.6%), constipation(12.7%), diarrhea(12.9%) and anorexia(10%). Determinants of self-reported ADEs among patients in the present study were body mass index above 25 (AOR: 2.55; 95%CI (1.21–5.38), p = 0.014), duration of acid-pepsin disorder more than 3weeks (AOR: 3.57; 95%CI (1.63–7.81), p = 0.001), pain feeling during long interval between meals (AOR: 2.14; 95%CI (1.19–3.84), p = 0.011), and residence in urban area (AOR: 1.95; 95% CI (1.04–3.67), p = 0.038).ConclusionSignificant proportion of patients reported ADEs which commonly manifested with gastrointestinal symptoms. Consideration of patients’ body mass index, duration of the disorder, period of the day when patients feel pain, and patients’ area of residence could help to reduce ADEs experienced during H. pylori eradication therapy.